ci: use gpt-5.4-mini and hang up live calls

[dimavrem22]

Summary

• use openai/gpt-5.4-mini for non-Realtime live intelligence while leaving Realtime media unchanged
• hang up every expected inbound and callback voice call through calls.hangup(callId) in finally
• snapshot calls owned by every live Vitest process, watchdog accidental calls in non-voice suites, and verify every new call is terminal during teardown
• require and lock @inkbox/sdk 0.4.24 for the external call-control API
• restore the inbound PSTN leg to required full-stack CI
• fail immediately when a call is already canceled or failed, and include any AUT SMS reply when a callback is not placed
• retain detailed inbound diagnostics

Root cause fixed

The voice test finished before the driver's delayed media stop frame, and teardown killed the driver. The carrier leg then remained alive until the ten-minute cap. Call records also proved that general channel jobs can unexpectedly choose the phone tool, so cleanup limited to voice.test.ts was insufficient.

Every live Vitest process now owns a baseline of calls. Non-voice suites stop any newly created call within the watchdog interval; voice tests retain direct per-call cleanup and use the session guard as a fallback.

Validation

• typecheck and lint passed
• 641 tests passed
• all live files load and skip cleanly without credentials
• workflow YAML and git diff --check passed